1. Field of the Invention
This invention is directed to the field of in vitro blood testing and, more particularly, to in vitro blood testing for determining the presence of a reaction in a patient's blood which would indicate whether the patient has a malady, such as an allergy, adverse reactions, sensitivity etc.
2. Description of the Related Art
Blood tests for diagnosing whether a patient is suffering from any of a variety of maladies have been around for many years. For example, cytotoxic testing and scratch testing have been used to determine whether an individual is sensitive to suspected allergens. These tests had many drawbacks. In vivo tests, such as scratch testing, involved exposing living subjects to potentially hazardous allergens. Known in vitro diagnostic testing could also be unreliable and inconsistently reproducible.
Beginning in the 1980's, the inventor herein began to develop more consistently repeatable methods for in vitro testing for food sensitivities and other maladies whose presence could be indicated by reactions with blood cells. For example, the inventor's own prior U.S. Pat. Nos. 4,614,722; 4,788,155; 5,147,785; 6,114,174; and 6,200,815, the disclosures of which are herein incorporated by reference as though set forth in full, disclose various methods of in vitro diagnostic blood tests.
Generally speaking, these patents are directed to methods and apparatus for detecting, measuring and evaluating responses of a patient's blood cells to exposure to potential reactants, such as suspected allergens, or other substances which could cause immune and/or none immune reactions. The inventor's prior work was based on his determination that blood cells (usually white blood cells, “wbcs”, but also red blood cells, “rbcs”, or platelets) react when in the presence of certain reactants. For example, when an individual is allergic to a particular food, if that individual's blood is exposed to that food, the blood reacts as though invaded by an infection—the blood cells may expand, release histamines, engulf the reactant or otherwise change size, including completely lysing, i.e., releasing of the cell's contents. By measuring the degree of size changes of the white blood cells, the nature and degree of reaction can be determined. The inventor's prior methods involved taking a sample of the patient's blood, and separating it into equal alequats of samples. One sample is not exposed to the potential reactants, or allergens, and that sample is used as a control sample. The other samples are exposed to differing potential reactants, or groups of reactants, and the cell counts of the control and test samples are compared to see if the test samples have different size distributions of blood cells than does the control sample.
But there are problems associated with the inventor's prior tests.
First, the blood cells that are the most sensitive to these type of reactions are the white blood cells. As described in the inventor's earlier work, and as is widely known, white blood cells and red blood cells are generally the same size, and red blood cells vastly outnumber white blood cells (by a multiple on the order of 500:1), so that attempts to measure reactions solely of the white blood cells in the presence of red blood cells is virtually impossible. The overwhelming number of red blood cells compared to white blood cells obscures any attempt to count white blood cells alone.
This problem is addressed in the inventor's prior work by lysing, i.e., destroying, the red blood cells by introducing a lysing agent into a sample of the patient's blood. After the red blood cells are lysed, the white blood cells may be counted. This leads to a different problem, however, since the same lysing agent that lyses red blood cells usually lyses white blood cells, as well, albeit more slowly.
Second, the inventor has now determined that different types of white blood cells exhibit different reactions to reactants, and that measuring the direction and degree of reactions of different types of white bloods may provide better information to permit more precise diagnoses for the patient. In prior testing, this pattern was not recognized, so that an increase in one type of white blood cell (e.g., monocytes) could mask a decrease in another type of white blood cell (e.g., eosinophils), so that the overall measurement could indicate no change in the overall size or distribution of white blood cells, while there were actually two different and complementary reactions, resulting in a false negative.